Treatment of minerals



Patented Aug. 29, 1933 TREATMENT OF MINERALS Eugene P. Schoch, Austin, Tex.

No Drawing. Application September 3,,1930 Serial .No. 479,5 81

6 Claims. (01. 23-38) My invention relates to the treatment ,of minerals and more particularly has reference to the removal of sodium chloride from ores containing other salts desired to be recovered. a

The mineral polyhalite (K2SO4,MgSOi,2CaSO4,2H2O) occurs in the form .of thin beds in the ground in parts. of west Texas and southeast New Mexico. While there are some beds of three to six feet in thickness which are, in general, almost. free from sodium chloride-containing only A, to thereof-yetsince they were all deposited from seawater between layers of sodium vchloride, it islikely that inclusions of the latter may occur anywhere, and-in other instances the sodium chloride is-actually dispersed through the polyhalite to any extent possible.

In my prior applications, :Serial Nos. 300,959,. 329,316 and 405,542, I have described and claimed esses of my prior applications, the potassium and.

magnesium sulphates are extracted in water solution from the ore while the. gypsum remainsas an insoluble residue.

I have found that the extraction of magnesium and potassium sulphates from polyhalitegk'rugite,

and like ores containing thesesalts is seriously complicated. when appreciable amounts of sodium chloride are also present, in-the ore, and since occasional inclusions of sodium chloride are to.

be expected in even the purest polyhalite occurring in nature, it is evidently necessary and dcsirable to be able to treat the (infer the removal of sodium chloride preliminarily tojth' extraction of the sulphates therefrom. Howeverfwhenplain wateris used to remove, sodium chloride,

the polyhalite or the like is appreciably attacked and serious losses ofpotassium sulphate, result. Thus, when a mixture or ore containing 20% of sodium chloride was leached with water tore- 7 move sodium chloride, the amount of potassium sulphate removed therewith amountedto 10 to 20% of the total potassiumsulphate present.

It is accordingly an object of the present invention to separate sodium' chloride from minerals or ores of the character referred to without materially affecting the ore and without entailing appreciable loss in the sulphates desired to be.

recovered from the ore. v

A further object of my invention resides in the removal of sodium chloride from polyhalite,

m'oveany admixed sodium" chloride from naturkrugite, and like'ores prepa ato y to th O lY of gypsum, potassium sulphate, and magnesium sulphate, forexample, in the manner described in ;my' prior, applicationsabove referred to, whereby the presence of sodium chloride does not inter- 6o fere with the recovery process. i

. It isa further object or the present invention to provide "a process of'thecharacter.referred to whichcis simple, economical andjefiicient in accomplishing its intended purposes, V

' Theoretically, the only way to prevent decontposition Of'a' mineral such as polyhalite'isto'bring r i it in contact with a solution containing all of its constituentsin just thosejconcentrations necessary for equilibrium between the mineral and 7 the solution. However, I have found that only a negligible amount of decomposition will take j place when polyhalite is incontact with water saturated with magnesium sulphate or with a concentrated solution of magnesium sulphate;

Furthermore, a saturated or concentrated so lution of magnesium sulphate will dissolve a certain amountof sodium chloride while precipitating only a slight amount of magnesium sulphate, this. taking place without the formation of any other product, For example, a solutionsaturated with magnesiumsulphateat 25 G. contains 54 mols'MgSOi-per 1000 mols H20 and. this solution canjidissolve 21.5 mols NazClz .while precipitat then Astracanite (MgSO .NaSO4.4I-IzO) is precipsuitable. operation;

Hence, by a .combinationof these facts llre- .al ,polyhalite and. like minerals .by leachingout the latter with a saturated or concentrated solu-'- tion of vrrlagnesium sulphate, preferably at about V 2570., using 'the latter in such proportion-that [95 the dissolved sodium chloride will not attain the concentration at which. astracanite formation will begin; In this manner the sodium salts may be entirely removed from polyhalite and the like? 1 I and yet extensive decomposition of the mineral avoided. g 1 g .In 'a particular'example, with an aggregate of",

77% polyhalite and 23%"sodium chloride, the latter was thus removed by leaching theaggregate. with the MgSO4 solution until the resulting mixture contained only ofone per cent. ofsodiu'n'i 1 I chloride and with a loss of potassium sulphate varying from 235% to 3.-0% of the whole po-' tassium sulphate present while leaching with water entails potash losses which are from three:

and one-halfjto eight times .asqgreat.

' quantity of sodium chloride.

' method of procedure:

I have also found that it is not necessary that the solution be initially absolutely saturated,

but merely so nearly so as to make it practically saturated after it has dissolve'd'the allowable um sulphate is precipitated, and the operation is a little moreeconomical in magnesium sulphate.- After the ore has been substantiallyfreed of admixed sodium chloride by leaching with a concentrated, saturated, or nearly saturated magnesium sulphate solution, it may be processed in any desired manner for the extraction of the.

soluble potassium and magnesium sulphates from the insoluble gypsum. I prefer, however, to carry v out the recovery process inaccordancewith the inventions of my prior applications referred to,

that is, by first roasting the ore and then extracting the soluble sulphates with hot or boiling Water.. By reason of the preliminary removal of J the sodium chloride, there are avoided serious complications in the recovery process which I have found aredue to the pre'senceof the chloride during the extraction of the sulphates.

The following exampleillustrates the preferred liquid was then filtered off, the residue was tvaSh'ed quickly with another portion'of solution-of the, same composition, the wash liquor removed by filtration, and the residue sucked as dry as 'possible. The residue on analysis by titration with AgNOs solution was'found tocontain only l1}.2 NaCl.- The combined leaching and washing solutions, weighing '76 gm. ,in'all, were found to'contain 0.76 grams K2804.

W This amounts to a K2804 removalamounting to v v .53 oi'lthe pure polyhalite'fwhile the salt col-item of the mixture was reduced from 6.3% t0 '0.24%.*

The proportions used above,.at;25 (Li-correspond to using a solution composed'of3 parts of. water to 1 part of anhydrous 'MgSO4;' of this" 3 solution, 9 parts serve to dissolve 1 part of so-' dium chloride. Y '1 The operation cannot be carried'out at tern;

perat'ures near 0 C.,' and belownor at "C.

and above-but'can be carried; out within-the solutions used must be somewhatmoreaconcen trated than that used above While'-attempera'-'- tures below-25 C. they must be more dilute. But

Thus no magnesi- I usual range of room temperatures, say 10to 35 0.; however. attemperatures above 25 C. the

in all cases, the ratio of MgSOtto-NaClto be dissolved remains practically the sameas may be seen from tables of solubility.

In practice, the operation is to be carried out substantially as here presented,namely,a definite amount of crushed ore with a known salt content is to be stirred together with such an amount of solution as corresponds to the directionsgiven above, and when the mixture has had adequatetime toreact the liquid is to be separated from the solid, and the latter washed. This whole operation can be made continuous by putting liquid and ore together in a long trough and propelling the solid forward at the same rate .a which the liquid flows forward.

If the relative amount of solution used is less than corresponds to the proportions above, astrakanite (MgSO4Na2SO4-1H2O) will be formed and precipitated; this isevidently to be avoided. If the relative amount of solution is greater, then no harm will result except that the operation will entail the use of more MgSOi.

' Althoughi have described the operation with considerable particularity, I do not wish this invention to belimited except as by'the scope of the appended claims. 6

Having described my invention, I claim:

1. The method of treating'polyhalite for the removal of sodium chloride -Which comprises leaching the ore with a concentrated solution of magnesium sulphate.

2. The method of treating polyhalite for the removal of sodium chloride which comprises leaching the ore with a saturated solution of magnesium sulphate. I '3'. The method of treating polyhalite for .the removal of sodium chloride which comprises leaching'the ore with a concentrated solution of magnesium sulphatein such proportion that the dissolv'ed'sodium chloride does no'tattain the concentration at which. astracanite formation oc-' curs; I

l -The method of treating polyhalite for the removal of sodium chloride which comprises leachingthe ore with a saturated solution of magnesium sulphate in such proportion that the 129 dissolved sodium chloride does not attain the concentration atwhich astracanite formation occurs.

151, In the extractionof soluble sulphates from polyhalite, the improvement which comprises re- 5 moving sodium chloride from the ore by leaching with a concentrated magnesium sulphate solution prior to the treatment of the ore for extraction .of the sulphates. V s V r J 6; The improvement as defined in claim 5 further characterized in. thatthe leaching is so controlled that the dissolved sodium chloridedoes not attain the concentration at which astracanite formation occurs. j

- EUGENE P.'SCHOCH. 

